TOWN OF GIBSON - Manitowoc County authorities are trying to determine who put a bomb in a backpack found in a ditch along a state highway.

A person found the backpack off State Highway 147 on Wednesday and alerted authorities. Deputies determined it to be an explosive device with a fuse that appeared to have been lit but didn't burn to the end.

Authorities say it appears the backpack was thrown from a moving vehicle but they don't know why.

Investigators are working to get fingerprint or DNA evidence from the backpack and its contents.